Variables analyzed in the test cohort for sacroiliitis (34 AS and 34 control patients). Patients with ankylosis were not analyzed for erosive or sclerotic changes.
| Variables | AS/control, n | Sn (95% CI) | Sp (95% CI) | LR+ (95% CI) | LR– (95% CI) |
|---|---|---|---|---|---|
| Ankylosis | 16/1 | 47.0 (30–65) | 97 (85–100) | 16 (2.2–114) | 0.6 (0.4–0.8) |
| Among patients without ankylosis, 18 AS and 33 control patients | |||||
| Any iliac erosions | 17/12 | 94 (73–100) | 63 (45–80) | 2.6 (1.6–4.1) | 0.1 (0.01–0.6) |
| Any sacral erosions | 14/6 | 78 (52–94) | 82 (65–93) | 4.3 (2–9.2) | 0.3 (0.1–0.7) |
| Total erosion score | |||||
| ≥ 1 erosion | 17/15 | 94 (73–100) | 55 (36–72) | 2.1 (1.4–3.1) | 0.1 (0.01–0.7) |
| ≥ 3 erosions | 15/2 | 83 (59–96) | 94 (80–99) | 13.8 (3.5–54) | 0.2 (0.06–0.5) |
| ≥ 5 erosions | 12/1 | 67 (41–87) | 97 (84–100) | 22.0 (3.1–156) | 0.3 (0.2–0.7) |
| Sclerosis | |||||
| Iliac depth > 0.3 cm | 17/22 | 94 (73–100) | 33 (18–52) | 1.4 (1.1–1.8) | 0.2 (0.02–1.2) |
| Iliac depth > 0.5 cm | 9/2 | 50 (26–74) | 94 (80–99) | 8.3 (2–34) | 0.5 (0.3–0.9) |
| Sacral depth > 0.3 cm | 5/0 | 28 (10–54) | 100 (89–100) | ∞ | 0.7 (0.5–1) |
| Sacral depth > 0.5 cm | 2/0 | 11 (1–35) | 100 (89–100) | ∞ | 0.9 (0.8–1) |
AS: ankylosing spondylitis; Sn: sensitivity; Sp: specificity; LR: likelihood ratio.